1. Field of the Invention
The present invention relates generally to a disk cartridge. Specifically, the present invention relates to a magneto-optical disk cartridge in which an overwrite type magneto-optical disk is provided and magnetic initializing means for generating a sufficient magnetic field for utilizing the overwrite type magneto-optical disk is provided within the cartridge casing.
2. Description of the Prior Art
Generally, magneto-optical disks require that old data be erased in one procedure before new data may be written. This erasure step is time consuming. Recently, an `overwrite` type magneto-optical disk has been developed in which it is possible to write new data directly over previously held data via a light intensity modulation method. Referring to FIGS. 6-8, such conventional and overwritable type magneto-optical disk cartridges and a disk drive arrangement for same will be explained hereinbelow.
FIG. 7, shows a disk drive 100 for magneto-optical disk cartridges and FIG. 6 shows a cutaway perspective view of a cartridge housing 1' mounting therein a conventional magneto-optical disk 10' and/or an overwritable disk cartridge 1" with an overwritable magneto-optical disk 10" mounted therein, both cartridge types being compatible with the disk drive 100 of FIG. 7. The conventional disk cartridge 10' has a single data layer according to a standard IOS construction and the overwritable magneto-optical disk 10" has a two layer construction according to the light intensity modulation method, in which a first data layer and a second rewrite layer are provided. Hereinbelow, for simplicity, both types of magneto-optical disks will be referred to by the numeral 10 and both types of cartridge by the numeral 1.
The disk drive 100, for utilizing the above described magneto-optical disk cartridges 1, includes a base frame, or chassis 101 having a spindle motor 102 mounted at a substantially center portion thereof for rotatably engaging the magneto-optical disk 10. For scanning the magneto-optical disk 10 in the radial direction thereof during read and/or write operation, a carriage 103 is provided with an optical pickup 104 mounted thereon. The carriage 103 is driven via a guide shaft (not shown) engaging a linear motor (not shown). Also mounted on the chassis 101 is a front panel 110. Above a chassis 101 is mounted a loading plate 111 which has a mounted slider (not shown) which is movable in forward and reverse and well as up and down directions for effecting loading of the magneto-optical disk cartridge 1. For supporting the magneto-optical disk cartridge 1 above the spindle motor 102, a cartridge holder 112 is provided at a lower side of the loading plate 111. Also provided is a sub-holder 113 for positioning the cartridge 1, at a position opposing the optical pickup 104, for scanning the magneto-optical disk 10 in the radial direction. The sub-holder 113 has mounted thereon a biasing magnet 114. Although not shown in the drawings, the sub-holder 113 is connected to a drive mechanism at a front side thereof for effecting upward and downward movement thereof. Also provided are an optical lens 105 mounted opposing the optical pickup 104, a optical setting portion 106 and a base plate 108.
Referring now to FIGS. 7 and 8, mounted at a position above the cartridge 1 a magnetic initializing means 115 is provided at a position which is above the upper surface of the magneto-optical disk 10. The sub-holder 113 may be stopped at a predetermined position in relation to the biasing magnet 114, which is an electromagnet, by a stop screw or the like. The magnetic initializing means 115 comprises a back yoke 115a having basically an inverted U shape for enhancing magnetic intensity and, mounted in a lower central portion thereof, an initializing magnet 115b is provided. By way of a driving mechanism (not shown) the magnetic initializing means 115 can be controlled so as to move adjacent to the casing 2 (see FIG. 6) of the cartridge 1, or to separate from the cartridge casing 2. Via the drive mechanism which brings the cartridge casing 2 into contact with the magnetic initializing means, a type of cartridge 1, that is, a conventional cartridge 1' or a overwritable cartridge 1", may be detected and the disk drive 100 may be set electronically and mechanically according to the detected disk type.
Specifically, if a surface magnetism-of 6000e or less is detected, it is assumed that a magnetic cartridge 1' housing a conventional magneto-optical disk 10' has been loaded and the magnetic initializing means 115 is moved to be remote from the casing 2 of the conventional magneto-optical disk cartridge 1'. Alternatively, when an overwritable magneto-optical disk cartridge 1" utilizing an overwritable magneto-optical disk 10" is loaded, the magnetic initializing means 115 is moved so as to be adjacent the outer surface of the casing 2 of the cartridge 1". In this condition, in the presence of a magnetic output kOe from the magnetic initializing means 115, only an overwritable type magneto-optical disk cartridge 1" can be utilized. A conventional magneto-optical disk cartridge 1' may not be read in this condition and, data on such a conventional magneto-optical disk 10' may be lost inadvertently.
Referring to FIG. 6, the construction of such magneto-optical disk cartridges 1' and 1" will be described hereinbelow. First, the casing 2 is generally comprised of a upper (first) shell 2a and a lower (second) shell 2b and the magneto-optical disk 10' or 10" is rotatably mounted between the upper and lower shells 2a and 2b. Openings 3, 3 are formed respectively in each of the upper and lower shells 2a and 2b at a position which opposes that of the optical pickup 104 when the cartridge 1 is loaded in the disk drive 100. Openings 3 are covered, when the cartridge 1 is not loaded, by a slidably disposed shutter 4 which is mounted on the outer side of the casing 2, astride the upper and lower shells 2a, 2b. Further, formed in the lower shell 2b, media sensor holes, such as an alignment hole 5, an A surface discriminating opening 6, a B surface discriminating opening 7, a gripper slot 8, a positioning hole 9, and the like, are provided.
Japanese Patent Application 4-173004 discloses a magneto-optical disk cartridge and disk drive therefore similar in construction to the above-described. According to this disclosure, when data is to be overwritten on a overwritable type magneto-optical disk cartridge 1" housing an overwritable magneto-optical disk 10", the magnetic initializing means 115 produces a magnetic output of 3-7 kOe and the magnetic polarity of the auxiliary layer of the overwritable magnetic disk 10" is set in a predetermined direction. After setting of the polarity direction of the auxiliary layer, on rotation of the magneto-optical disk 10", the bias magnet 114, which is mounted at a position directly over the optical pickup 104, is active to invert the output of the magnetic initializing means so as to produce a bias magnetic field of 200-400 Oe required by the overwritable magneto-optical disk 10". The object lens 105 of the optical pickup 104 is active to output a laser beam onto the surface layer of the overwritable magneto-optical disk 10" so as to neutralize the magnetic polarity of the surface layer (laser irradiation at a temperature above Curie temperature). During and during a cooling period after irradiation, the direction of magnetic polarity of the surface layer is determined and writing of data is accomplished. Further, according to the above, an improvement is available in that a relatively weak laser may be used for writing an a magnetic polarity of the surface layer is altered according to the polarity of light during laser irradiation.
Further, when a conventional magneto-optical disk cartridge 1' utilizing a conventional magneto-optical disk 10' is to be utilized in the disk drive 100, the drive mechanism is active beforehand to move the magnetic initializing means 115 away from the cartridge 1' to prevent the strong magnetic field thereof from influencing the conventional magneto-optical disk 10'. Then the reading and/or writing operation is carried out via the bias field of the bias magnet 114 and the optical pickup 104.
However according to such arrangements for utilizing overwritable magneto-optical disks 10" in a cartridge 1" to be loaded in a disk drive 100. Since a relatively large magnet must be utilized in order to produce the approximately 3 kOe magnetic field of the magnetic initializing means 115, and the magnetic initializing means must have room to be moved toward and away from a disk cartridge 1 which is loaded into the disk drive 100, the weight of the disk drive is increased and the `dead space` required for movement thereof increases the necessary thickness of the disk drive unit. Also, the above imperatives along with the driving mechanism required for the magnetic initializing means cause cost of the disk drive unit to increase. Thus, there is a need to provide an overwritable magneto-optical disk cartridge which may be utilized in a manner allowing a reduction in the weight, thickness and cost of the disk drive unit.